Density phase separation device

ABSTRACT

A mechanical separator for separating a fluid sample into first and second phases is disclosed. The mechanical separator includes a float having a first portion and a second portion, a ballast circumferentially disposed about a section of the float, and a deformable bellows defining an open passageway extending between a first end and a second end. The ballast is longitudinally moveable with respect to the float and engaged with the deformable bellows between the first end and the second end. At least a portion of the float is transitionable from a restraint position to a sealed position through the first end of the bellows. The first portion of the float can be positioned within the interior of the deformable bellows in the restraint position, and the first portion of the float can be positioned at an exterior location longitudinally displaced from the deformable bellows in the sealed position.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 61/082,361, filed Jul. 21, 2008, entitled “Density Phase SeparationDevice”, the entire disclosure of which is herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention relates to a device and method for separatingheavier and lighter fractions of a fluid sample. More particularly, thisinvention relates to a device and method for collecting and transportingfluid samples whereby the device and fluid sample are subjected tocentrifugation in order to cause separation of the heavier fraction fromthe lighter fraction of the fluid sample.

2. Description of Related Art

Diagnostic tests may require separation of a patient's whole bloodsample into components, such as serum or plasma, (the lighter phasecomponent), and red blood cells, (the heavier phase component). Samplesof whole blood are typically collected by venipuncture through a cannulaor needle attached to a syringe or an evacuated blood collection tube.After collection, separation of the blood into serum or plasma and redblood cells is accomplished by rotation of the syringe or tube in acentrifuge. In order to maintain the separation, a barrier must bepositioned between the heavier and lighter phase components. This allowsthe separated components to be subsequently examined.

A variety of separation barriers have been used in collection devices todivide the area between the heavier and lighter phases of a fluidsample. The most widely used devices include thixotropic gel materials,such as polyester gels. However, current polyester gel serum separationtubes require special manufacturing equipment to both prepare the geland fill the tubes. Moreover, the shelf-life of the product is limited.Over time, globules may be released from the gel mass and enter one orboth of the separated phase components. These globules may clog themeasuring instruments, such as the instrument probes used during theclinical examination of the sample collected in the tube. Furthermore,commercially available gel barriers may react chemically with theanalytes. Accordingly, if certain drugs are present in the blood samplewhen it is taken, an adverse chemical reaction with the gel interfacecan occur.

Certain mechanical separators have also been proposed in which amechanical barrier can be employed between the heavier and lighterphases of the fluid sample. Conventional mechanical barriers arepositioned between heavier and lighter phase components utilizingdifferential buoyancy and elevated gravitational forces applied duringcentrifugation. For proper orientation with respect to plasma and serumspecimens, conventional mechanical separators typically require that themechanical separator be affixed to the underside of the tube closure insuch a manner that blood fill occurs through or around the device whenengaged with a blood collection set. This attachment is required toprevent the premature movement of the separator during shipment,handling and blood draw. Conventional mechanical separators are affixedto the tube closure by a mechanical interlock between the bellowscomponent and the closure. Example devices are described in U.S. Pat.Nos. 6,803,022 and 6,479,298.

Conventional mechanical separators have some significant drawbacks. Asshown in FIG. 1, conventional separators include a bellows 34 forproviding a seal with the tube or syringe wall 38. Typically, at least aportion of the bellows 34 is housed within, or in contact with a closure32. As shown in FIG. 1, as the needle 30 enters through the closure 32,the bellows 34 is depressed. This creates a void 36 in which blood maypool when the needle 30 is removed. This can result in needle clearanceissues, sample pooling under the closure, device pre-launch in which themechanical separator prematurely releases during blood collection,hemolysis, fibrin draping and/or poor sample quality. Furthermore,previous mechanical separators are costly and complicated to manufacturedue to the complicated multi-part fabrication techniques.

Accordingly, a need exists for a separator device that is compatiblewith standard sampling equipment and reduces or eliminates theaforementioned problems of conventional separators. A need also existsfor a separator device that is easily used to separate a blood sample,minimizes cross-contamination of the heavier and lighter phases of thesample during centrifugation, is independent of temperature duringstorage and shipping and is stable to radiation sterilization.

SUMMARY OF THE INVENTION

The present invention is directed to an assembly and method forseparating a fluid sample into a higher specific gravity phase and alower specific gravity phase. Desirably, the mechanical separator of thepresent invention may be used with a tube, and the mechanical separatoris structured to move within the tube under the action of appliedcentrifugal force in order to separate the portions of a fluid sample.Most preferably, the tube is a specimen collection tube including anopen end, a closed end or an apposing end, and a sidewall extendingbetween the open end and closed end or apposing end. The sidewallincludes an outer surface and an inner surface and the tube furtherincludes a closure disposed to fit in the open end of the tube with are-sealable septum. Alternatively, both ends of the tube may be open,and both ends of the tube may be sealed by elastomeric closures. Atleast one of the closures of the tube may include a needle pierceablere-sealable septum.

The mechanical separator may be disposed within the tube at a locationbetween the top closure and the bottom of the tube. The separatorincludes opposed top and bottom ends and includes a float, a ballast,and a deformable bellows. The components of the separator aredimensioned and configured to achieve an overall density for theseparator that lies between the densities of the phases of a fluidsample, such as a blood sample.

In one embodiment, the mechanical separator for separating a fluidsample into first and second phases within a tube includes a floathaving a first portion and a second portion, and a ballastcircumferentially disposed about a section of the float andlongitudinally moveable with respect to the float. The mechanicalseparator also includes a deformable bellows defining an open passagewayextending between a first end and a second end. The ballast of themechanical separator is engaged with the deformable bellows between thefirst end and the second end, and at least a portion of the floattransitionable from a restraint position to a sealed position throughthe first end of the deformable bellows. The first portion of the floatmay be positioned within the interior of the deformable bellows in therestraint position, and the first portion of the float may be positionedat an exterior location longitudinally displaced from the deformablebellows in the sealed position. The float may have a first density, andthe ballast may have a second density greater than the first density ofthe float.

The mechanical separator may be oriented such that the first portion ofthe float may be positioned below the first end of the deformablebellows in the restraint position, and the first portion of the floatmay be positioned above the first end of the deformable bellows in thesealed position. Transition of the float from the restraint position tothe sealed position may occur as the float and ballast exert opposingforces on the deformable bellows allowing the float to be receivedwithin the deformable bellows. The float may include an engagementprotrusion, and the deformable bellows may include a restraint shoulder.The engagement protrusion of the float may be releaseably restrainedwithin the deformable bellows by the restraint shoulder. In the sealedposition, the float and the deformable bellows may form a liquidimpermeable seal.

The float may also include a head portion and a body portion. The bodyportion of the float may include a first section having a first diameterand a second stepped section having a second diameter, the seconddiameter greater than the first diameter. The float may also be made ofa solid material.

The ballast may include an interlock recess for accommodating a portionof the deformable bellows for attachment thereto. The ballast may alsoinclude an exterior surface and define an annular shouldercircumferentially disposed within the exterior surface.

Optionally, at least a portion of the first end of the deformablebellows may be structured for receipt within a closure. Further, atleast a portion of the first end of the deformable bellows may bestructured to receive a portion of the closure therein.

The float of the mechanical separator may be made of polypropylene, theballast may be made of polyethylene terephthalate, and the deformablebellows may be made of a thermoplastic elastomer.

In another embodiment, a mechanical separator includes a float having afirst portion and a second portion, and a ballast circumferentiallydisposed about a portion of the float and longitudinally moveable withrespect to the float. The mechanical separator also includes adeformable bellows having an open first end and an open second end anddefining an open passageway extending therebetween. The deformablebellows includes an exterior surface engaged with a portion of theballast, and an interior surface releaseably engaged with a portion ofthe float. The float may have a first density, and the ballast may havea second density greater than the first density of the float.

Optionally, at least a portion of the float is transitionable from arestraint position to a sealed position through the first end of thedeformable bellows. The first portion of the float may be positionedwithin the interior of the deformable bellows in the restraint position,and the first portion of the float may be positioned at an exteriorlocation longitudinally displaced from the deformable bellows in thesealed position. Transition of the float from the restraint position tothe sealed position may occur as the float and ballast exert opposingforces on the deformable bellows allowing the float to be receivedwithin the deformable bellows. The mechanical separator may be orientedsuch that the first portion of the float may be positioned below thefirst end of the deformable bellows in the restraint position, and thefirst portion of the float may be positioned above the first end of thedeformable bellows in the sealed position. In the sealed position, thefloat and the deformable bellows form a liquid impermeable seal. In oneconfiguration, the float may include an engagement protrusion and thedeformable bellows may include a restraint shoulder. The engagementprotrusion of the float may be releaseably restrained within thedeformable bellows by the restraint shoulder.

In another embodiment, a separation assembly for enabling separation ofa fluid sample into first and second phases, includes a tube having anopen end, a closed end or an apposing end, and a sidewall extendingtherebetween. A closure adapted for sealing engagement with the open endof the tube is also included. The closure defines a recess, and amechanical separator is releaseably engaged within the recess. Themechanical separator includes a float having a first portion and asecond portion, and a ballast circumferentially disposed about a sectionof the float and longitudinally moveable with respect to the float. Themechanical separator also includes a deformable bellows defining an openpassageway extending between a first end and a second end. The ballastof the mechanical separator is engaged with the deformable bellowsbetween the first end and the second end, and at least a portion of thefloat transitionable from a restraint position to a sealed positionthough the first end of the deformable bellows. The first portion of thefloat may be positioned within the interior of the deformable bellows inthe restraint position, and the first portion of the float may bepositioned at an exterior location longitudinally displaced from thedeformable bellows in the sealed position. The float may have a firstdensity, and the ballast may have a second density greater than thefirst density of the float.

The separation assembly may be oriented such that the first portion ofthe float may be positioned below the first end of the deformablebellows in the restraint position, and the first portion of the floatmay be positioned above the first end of the deformable bellows in thesealed position. Transition of the float from the restraint position tothe sealed position may occur upon longitudinal deformation of thedeformable bellows.

In yet another embodiment, a separation assembly for enabling separationof a fluid sample into first and second phases includes a tube, havingan open end, a closed end or an apposing end, and a sidewall extendingtherebetween. A closure adapted for sealing engagement with the open endof the tube is also included. The closure defines a recess, and amechanical separator is releaseably engaged within the recess. Themechanical separator includes a float having a first portion and asecond portion, and a ballast circumferentially disposed about a portionof the float and longitudinally moveable with respect to the float. Themechanical separator also includes a deformable bellows having an openfirst end and an open second end and defining an open passagewayextending therebetween. The deformable bellows includes an exteriorsurface engaged with a portion of the ballast, and an interior surfacereleaseably engaged with a portion of the float. The float may have afirst density, and the ballast may have a second density greater thanthe first density of the float.

In one configuration, at least a portion of the float is transitionablefrom a restraint position to a sealed position through the first end ofthe deformable bellows. The first portion of the float may be positionedwithin the interior of the deformable bellows in the restraint position,and the first portion of the float may be positioned at an exteriorlocation longitudinally displaced from the deformable bellows in thesealed position. Transition from the restraint position to the sealedposition may occur upon longitudinal deformation of the deformablebellows.

In another embodiment, a method of separating a fluid sample intolighter and heavier phases within a tube includes the step of subjectinga separation assembly having a fluid sample disposed therein toaccelerated rotational forces. The separation assembly includes a tube,having an open end, a closed end or an apposing end, and a sidewallextending therebetween. The separation assembly also includes a closureadapted for sealing engagement with the open end of the tube, with theclosure defining a recess. The separation assembly further includes amechanical separator releaseably engaged within the recess. Themechanical separator includes a float having a first portion and asecond portion, a ballast circumferentially disposed about a section ofthe float and longitudinally moveable with respect to the float, and adeformable bellows engaged with a portion of the sidewall. Thedeformable bellows defines an open passageway extending between a firstend and a second end, with the ballast engaged with the deformablebellows between the first end and the second end. At least a portion ofthe float is transitionable from a restraint position to a sealedposition through the first end of the deformable bellows. The methodfurther includes the steps of disengaging the mechanical separator fromthe closure, and venting air from within the mechanical separatorthrough the open passageway of the deformable bellows until themechanical separator is submerged within the fluid. The method alsoincludes the steps of elongating the deformable bellows to at leastpartially separate from the sidewall, and transitioning the float fromthe restraint position to the sealed position.

The assembly of the present invention is advantageous over existingseparation products that utilize separation gel. In particular, theassembly of the present invention is more favorable than gel with regardto minimizing and does not interfere with analytes resulting from sampleseparation. Another attribute of the present invention is that theassembly of the present invention is more favorable than prior art withregard to minimizing interference with therapeutic drug monitoringanalytes.

The assembly of the present invention is also advantageous over existingmechanical separators in that the deformable bellows of the mechanicalseparator is snapped over a boss that protrudes from the underside ofthe closure, which provides retention and launch load control. As such,the deformable bellows does not directly interface with the underside ofthe closure in the region where the needle exits the closure. Pre-launchis therefore minimized by eliminating the deformable bellows from thepath of the collection needle. This further minimizes sample poolingunder the closure, hemolysis, fibrin draping, and/or poor samplequality. Additionally, the assembly of the present invention does notrequire complicated extrusion techniques during fabrication and mayemploy two-shot molding techniques.

In accordance with yet another embodiment of the present invention, aseparation assembly for enabling separation of a fluid sample into firstand second phases includes a tube having an open end, an apposing end,and a sidewall extending therebetween. The separation assembly alsoincludes a closure adapted for sealing engagement with the open end ofthe tube and a mechanical separator disposed within the tube. Themechanical separator includes a float having a first portion and asecond portion, with the float having a first density. The mechanicalseparator also includes a ballast disposed about a portion of the floatand longitudinally moveable with respect to the float, with the ballasthaving a second density greater than the first density of the float. Themechanical separator further includes a deformable bellows interfacedwith the float, with the bellows having an open first end and an opensecond end and defining an open passageway extending therebetween. Thedeformable bellows includes an exterior surface engaged with a portionof the ballast, and an interior surface releaseably engaged with aportion of the float, wherein centrifugal force is applied to theseparation assembly when filled with fluid components of localizeddensities ranging from less than the density of the float and greaterthan the density of the ballast, and wherein sufficient centrifugalforces can seat the bellows onto the float.

Further details and advantages of the invention will become clear fromthe following detailed description when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional side view of a conventionalmechanical separator.

FIG. 2 is an exploded perspective view of a mechanical separationassembly including a closure, a deformable bellows, a ballast, a float,and a collection tube in accordance with an embodiment of the presentinvention.

FIG. 3 is a cross-sectional front view of the closure of FIG. 2.

FIG. 4 is a perspective view of the float of FIG. 2.

FIG. 5 is a front view of the float of FIG. 2.

FIG. 6 is a perspective view of the ballast of FIG. 2.

FIG. 7 is a front view of the ballast of FIG. 2.

FIG. 8 is a cross-sectional view of the ballast of FIG. 2 taken alongline 8-8 of FIG. 7.

FIG. 9 is a close-up cross-sectional view of the ballast of FIG. 2 takenalong section IX of FIG. 8.

FIG. 10 is a front view of the deformable bellows of FIG. 2.

FIG. 11 is a cross-sectional view of the deformable bellows of FIG. 2taken along line 11-11 of FIG. 10.

FIG. 12 is a side view of the deformable bellows of FIG. 2.

FIG. 13 is a cross-sectional view of the deformable bellows of FIG. 2taken along line 13-13 of FIG. 12.

FIG. 14 is a perspective view of the assembled mechanical separator ofFIG. 2 in the restraint position.

FIG. 15 is a cross-sectional view of the assembled mechanical separatorengaged with the closure of FIG. 2 in the restraint position.

FIG. 16 is a front view of an assembly including a tube having a closureand a mechanical separator disposed therein in accordance with anembodiment of the present invention.

FIG. 17 is a cross-sectional front view of the assembly of FIG. 16having a needle accessing the interior of the tube and an amount offluid provided through the needle into the interior of the tube inaccordance with an embodiment of the present invention.

FIG. 18 is a cross-sectional front view of the assembly of FIG. 17having the needle removed therefrom during use and the mechanicalseparator positioned apart from the closure in accordance with anembodiment of the present invention.

FIG. 19 is a perspective view of the assembled mechanical separator ofFIG. 2 in the sealed position.

FIG. 20 is a front view of the assembled mechanical separator of FIG. 2in the sealed position.

FIG. 21 is a cross-sectional view of the assembled mechanical separatorof FIG. 2 in the sealed position taken along line 21-21 of FIG. 20.

FIG. 22 is a cross-sectional front view of the assembly of FIG. 18having the mechanical separator separating the less dense portion of thefluid from the denser portion of the fluid in accordance with anembodiment of the present invention.

FIG. 23 is a cross-sectional view of an alternative mechanical separatorengaged with a conventional stopper in the restraint position inaccordance with an embodiment of the present invention.

FIG. 24 is a cross-sectional view of the mechanical separator disengagedwith the conventional stopper of FIG. 23 in the sealed position inaccordance with an embodiment of the present invention.

FIG. 25 is a cross-sectional view of a mechanical separator engaged witha conventional stopper and luer collar in the restraint position inaccordance with an embodiment of the present invention.

FIG. 26 is a cross-sectional view of the mechanical separator disengagedwith the conventional stopper and luer collar of FIG. 25 in the sealedposition in accordance with an embodiment of the present invention.

FIG. 27 is a partial cross-sectional partially exploded perspective viewof a mechanical separation assembly including a closure, a mechanicalseparator in the sealed position, a tube insert, and a collection tubein accordance with an embodiment of the present invention.

FIG. 28 is a partial cross-sectional front view of a mechanicalseparation assembly including a closure, a closure insert, a mechanicalseparator in the restraint position, and a collection tube in accordancewith an embodiment of the present invention.

FIG. 29 is a cross-sectional view of a mechanical separator including afloat, a deformable bellows having restraining shoulders, and a ballastin the restrained position with a closure in accordance with anembodiment of the present invention.

FIG. 30 is a cross-sectional view of the mechanical separator of FIG. 29in the sealed position.

FIG. 31 is a cross-sectional view of a mechanical separator including analternative float, a deformable bellows, and a ballast in the restrainedposition with a closure in accordance with an embodiment of the presentinvention.

FIG. 32 is a cross-sectional view of the mechanical separator of FIG. 31in the sealed position.

FIG. 33 is a cross-sectional view of a mechanical separator including aspherical float, a deformable bellows, and a ballast in the restrainedposition with a closure in accordance with an embodiment of the presentinvention.

FIG. 34 is a cross-sectional view of the mechanical separator of FIG. 33in the sealed position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of the description hereinafter, the words “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”,“longitudinal” and like spatial terms, if used, shall relate to thedescribed embodiments as oriented in the drawing figures. However, it isto be understood that many alternative variations and embodiments may beassumed except where expressly specified to the contrary. It is also tobe understood that the specific devices and embodiments illustrated inthe accompanying drawings and described herein are simply exemplaryembodiments of the invention.

As shown in exploded perspective view in FIG. 2, the mechanicalseparation assembly 40 of the present invention includes a closure 42with a mechanical separator 44, for use in connection with a tube 46 forseparating a fluid sample into first and second phases within the tube46. The tube 46 may be a sample collection tube, such as a proteomics,molecular diagnostics, chemistry sample tube, blood or other bodilyfluid collection tube, coagulation sample tube, hematology sample tube,and the like. The tube 46 may also contain additional additives asrequired for a particular tube function. For example, the tube 46 maycontain a clot inhibiting agent, clotting agents, and the like. Theseadditives may be provided in particle or liquid form and may be sprayedonto the tube 46 or located at the bottom of the tube 46. Desirably,tube 46 is an evacuated blood collection tube. The tube 46 may include aclosed or an apposing bottom end 48, an open top end 50, and acylindrical sidewall 52 extending therebetween. The cylindrical sidewall52 includes an inner surface 54 with an inside diameter “a” extendingsubstantially uniformly from the open top end 50 to a locationsubstantially adjacent the closed bottom end 48.

The tube 46 may be made of one or more than one of the followingrepresentative materials: polypropylene, polyethylene terephthalate(PET), glass, or combinations thereof. The tube 46 can include a singlewall or multiple wall configurations. Additionally, the tube 46 may beconstructed in any practical size for obtaining an appropriatebiological sample. For example, the tube 46 may be of a size similar toconventional large volume tubes, small volume tubes, or microtainertubes, as is known in the art. In one particular embodiment, the tube 46may be a standard 3 ml evacuated blood collection tube, or an 8.5 mlblood draw tube having a 16 mm diameter and a length of 100 mm, as isalso known in the art.

The open top end 50 is structured to at least partially receive theclosure 42 therein to form a liquid impermeable seal. The closureincludes a top end 56 and a bottom end 58 structured to be at leastpartially received within the tube 46. Portions of the closure 42adjacent the top end 56 define a maximum outer diameter which exceedsthe inside diameter “a” of the tube 46.

As shown in FIGS. 2-3, portions of the closure 42 at the top end 56include a central recess 60 which define a pierceable re-sealableseptum. Portions of the closure 42 extending downwardly from the bottomend 58 may taper from a minor diameter which is approximately equal to,or slightly less than, the inside diameter “a” of the tube 46 to a majordiameter that is greater than the inside diameter “a” of the tube 46.Thus, the bottom end 58 of the closure 42 may be urged into a portion ofthe tube 46 adjacent the open top end 50. The inherent resiliency ofclosure 42 can insure a sealing engagement with the inner surface of thecylindrical sidewall 52 of the tube 46.

In one embodiment, the closure 42 can be formed of a unitarily moldedrubber or elastomeric material, having any suitable size and dimensionsto provide sealing engagement with the tube 46. The closure 42 can alsobe formed to define a bottom recess 62 extending into the bottom end 58.The bottom recess 62 may be sized to receive at least a portion of themechanical separator 44. In one embodiment, the bottom end 58 of theclosure 42 includes a graduated boss portion 64, which extends from thebottom end 58 of the closure 42 for engagement with the mechanicalseparator 44. The graduated boss portion 64 of the closure may includean outer ridge 68 and an inner surface 70 disposed within the outerridge 68. In one embodiment, the boss portion 64 may extend into aportion of the mechanical separator 44. Additionally, a plurality ofspaced apart arcuate flanges 66 may extend around the bottom recess 62to at least partially restrain the mechanical separator 44 therein. Inone embodiment, the flanges 66 are continuous about the circumference ofthe bottom recess 62.

Optionally, the closure 42 may be at least partially surrounded by ashield, such as a Hemogard® Shield commercially available from Becton,Dickinson and Company, to shield the user from droplets of blood in theclosure 42 and from potential blood aerosolisation effects when theclosure 42 is removed from the tube 46, as is known.

Referring again to FIG. 2, the mechanical separator 44 includes a float72, a ballast 74, and a deformable bellows 76 such that the ballast 74is engaged with a portion of the deformable bellows 76 and the float 72is also engaged with a portion of the deformable bellows 76.

Referring to FIGS. 4-5, the float 72 of the mechanical separator is agenerally tubular body having an upper end 80 and a lower end 82. Theupper end 80 of the float 72 may include a head portion 84 separatedfrom the lower end 82 by an engagement protrusion 86. In one embodiment,the head portion 84 is separated from the engagement protrusion 86 by aneck portion 88. The lower end 82 of the float 72 may include a bodyportion 90 having a first section 92 and a second stepped section 94graduated from the first section 92.

In one embodiment, the outer diameter “b” of the second stepped section94 is less than the inside diameter “a” of the tube 46, shown in FIG. 2.In another embodiment, the outer diameter “c” of the first section 92 isless than the outer diameter “b” of the second stepped section 94. Theouter diameter “d” of the head portion 84 is typically less than theouter diameter “c” of the first section 92 or the outer diameter “b” ofthe second stepped section 94. The outer diameter “e” of the engagementprotrusion 86 is greater than the outer diameter “d” of the head portion84. In one embodiment, the outer diameter “e” of the engagementprotrusion 86 is less than the outer diameter “b” of the second steppedsection 94. In another embodiment, the outer diameter “b” and the outerdiameter “e” are the same size.

In one embodiment, the head portion 84 has a generally curved shape,such as having a curvature substantially corresponding to the curvatureof the boss portion 64, shown in FIG. 3. In another embodiment, the headportion 84 has a curvature substantially corresponding to the curvatureof the inner surface 70 of the boss portion 64, also shown in FIG. 3.The curvature of the head portion 84 may facilitate shedding of cells orother biological material during centrifugation.

The float 72 can be substantially symmetrical about a longitudinal axisL. In one embodiment, it is desirable that the float 72 of themechanical separator 44 be made from a material having a density lighterthan the liquid intended to be separated into two phases. For example,if it is desired to separate human blood into serum and plasma, then itis desirable that the float 72 have a density of no more than about0.902 gm/cc. In one embodiment, the float 72 can be made of a solidmaterial, such as polypropylene.

As shown in FIGS. 6-9, the ballast 74 of the mechanical separator 44includes an upper end 124 and a lower end 126 with a generallycylindrical section 120 extending therebetween. In one embodiment, theballast 74 includes an interior surface 122 structured to engage atleast a portion of the deformable bellows 76, shown in FIG. 2. Inanother embodiment, the upper end 124 includes a recess 128 forreceiving a portion of the deformable bellows 76, also shown in FIG. 2,therein.

The outer diameter “j” of the ballast 74 is less than the insidediameter “a” of the tube 46, shown in FIG. 2, therefore, the ballast 74may freely slide within the tube 46. The inside diameter “i” of therecess 128 is less than the outer diameter “j” of the ballast 74, andcan have any dimensions suitable to receive a portion of the deformablebellows 76, also shown in FIG. 2. The inner diameter “k” of the interiorsurface 122 of the ballast 74 is also greater than the outer diameter“b” of the second stepped section 94 of the float 72, shown in FIGS.4-5. Accordingly, the float 72 may freely move within the interior ofthe ballast 74. In one embodiment, the ballast is circumferentiallydisposed about at least a portion of the float 72. In yet anotherembodiment, the ballast 74 is longitudinally moveable with respect tothe float 72.

As shown in FIG. 7, in one embodiment, the ballast 72 may include amechanical interlock recess 130 extending through the generallycylindrical section 120, such as adjacent the upper end 124. In anotherembodiment, the ballast 72 may include the mechanical interlock recess130 within an interior wall 131 for engagement with a portion of thedeformable bellows 76, such as for accommodating a portion of thedeformable bellows 76 for attachment thereto. In a further embodiment,the interlock recess 130 is located in recess 128.

In one embodiment, it is desirable that the ballast 74 of the mechanicalseparator 44 be made from a material having a density heavier than theliquid intended to be separated into two phases. For example, if it isdesired to separate human blood into serum and plasma, then it isdesirable that the ballast 74 have a density of at least 1.326 gm/cc. Inone embodiment, the ballast 74 may have a density that is greater thanthe density of the float 72, shown in FIGS. 4-5. In another embodiment,the ballast 74 can be formed from PET.

As shown in FIGS. 6-9, the exterior surface of the ballast 74 may definean annular recess 134 circumferentially disposed about a longitudinalaxis L₁ of the ballast 72, and extending into the exterior surface ofthe cylindrical section 120. In this embodiment, the annular recess 134is structured to allow for an automated assembly to engage the ballast74 with the deformable bellows 76 and/or float 72, shown in FIG. 2.

As shown in FIGS. 10-13, the deformable bellows 76 of the mechanicalseparator 44 includes an upper first end 136 and a lower second end 138with an open passageway 142 extending therebetween. The upper first end136 includes a deformable sealing portion 140 circumferentially disposedabout the open passageway 142 for providing sealing engagement with thecylindrical sidewall 52 of the tube 46, shown in FIG. 2. The deformablesealing portion 140 can be positioned substantially adjacent the uppersurface 144 of the upper first end 136 of the deformable bellows 76. Thedeformable sealing portion 140 may have a generally torodial shapehaving an outside diameter “k” which, in an unbiased position, slightlyexceeds the inside diameter “a” of the tube 46, shown in FIG. 2.However, oppositely directed forces on the upper first end 136 and thelower second end 138 of the deformable bellows 76 will lengthen thedeformable sealing portion 140, simultaneously reducing the outerdiameter “k” to a dimension less than “a”. Likewise, the open passageway142 has an inner diameter “m” which, in an unbiased position, is smallerthan the outer diameter “d” of the head portion 84 of the float 72,shown in FIG. 5. Oppositely directed forces on the upper first end 136and the lower second end 138 of the deformable bellows 76 will increasethe inner diameter “m” of the open passageway to a diameter exceedingthe outer diameter “d” of the head portion 84 of the float 72, againshown in FIG. 5.

The deformable bellows 76, including the deformable sealing portion 140,is substantially symmetrical (with the possible exception of theplacement of protrusions 160) about a longitudinal axis L₂, and can bemade of any sufficiently elastomeric material sufficient to form aliquid impermeable seal with the cylindrical sidewall 52 of the tube 46,shown in FIG. 2. In one embodiment, the deformable bellows 76 is made ofa thermoplastic elastomer, such as thermoplastic polypropylene and hasan approximate dimensional thickness of from about 0.020 inch to about0.050 inch. In another embodiment, the entire bellows structure 70 ismade of thermoplastic elastomer.

In one embodiment, the upper first end 136 of the deformable bellows 76includes an annular shoulder 146 extending into the interior 148 of thedeformable bellows 76 adjacent the deformable sealing portion 140. Inanother embodiment, the annular shoulder 146 may be an interior surface152 of the upper first end 136 of the deformable bellows 76. Preferably,the annular shoulder 146 is positioned longitudinally above at least aportion of the deformable sealing portion 140. Alternatively, theannular shoulder 146 may be an interior surface 152 of the upper portionof the deformable sealing portion 140. In one embodiment, the deformablebellows 76 includes a recess 150 extending at least partially into theinterior surface 152 of the upper first end 136. The recess 150 may becircumferentially disposed about the open passageway 142, and may be acontinuous recess or a partitioned recess. The recess 150 may reduce thespring constant of the deformable bellows 76, allowing the deformablebellows 76 to longitudinally deform with less applied force. In oneembodiment, this may be accomplished by reducing the wall section of thedeformable bellows 76 to create a hinge.

In addition, at least a portion of deformable bellows 76, such as theupper first end 136, can be structured for receipt within the closure42, such as the bottom recess 62, also shown in FIGS. 2-3. In oneembodiment, at least a portion of the deformable sealing portion 140 ofthe deformable bellows 76 is structured for receipt within the bottomrecess 62 of the closure 42.

The lower second end 138 of the deformable bellows 76 includes opposeddepending portions 154 extending longitudinally downward from the upperfirst end 136. In one embodiment, the opposed depending portions 154 areconnected to a lower end ring 156 extending circumferentially about theopen passageway 142 and below the deformable sealing portion 140. In oneembodiment, the opposed depending portions 154 include at least oneballast interlock protrusion 158 extending from a portion of theexterior surface 160. The interlock protrusion 158 is engageable withthe interlock recess 130 of the ballast 74, shown in FIGS. 6-9, tosecure the ballast 74 to a portion of the deformable bellows 76 betweenthe upper first end 136 and the lower second end 138. Optionally, theinterlock recess 130 of the ballast 74 may extend completely through theopposing wall of the ballast 74. In one embodiment, the exterior surface160 of the deformable bellows 76 is secured with the interior wall 131of the ballast 74, shown in FIGS. 6-9. In one embodiment, two-shotmolding techniques may be used to secure the deformable bellows 76 tothe ballast 74.

The lower second end 138 of the deformable bellows 76 may also include arestraint shoulder 162 extending into the interior 148 of the deformablebellows 76. The restraint shoulder 162 may be positioned at the bottomend 163 of the opposed depending portions 154. In one embodiment, theinterior 148 of the deformable bellows 76 is structured to releaseablyretain at least a portion of the float 72, shown in FIGS. 4-5, therein.In another embodiment, the restraint shoulder 162 is structured torestrain the engagement protrusions 86 of the float 72 thereagainst, anddimensioned to allow a portion of the float 72, such as the head portion84 to pass into the interior 148 of the deformable bellows 76. The innerdiameter “n” of the deformable bellows adjacent the lower second end138, such as extending between the restraint shoulder 162, isdimensioned to be greater than the inner diameter “m” of the openpassageway 142, but smaller than the outer diameter “e” of theengagement protrusion 86 of the float 72, shown in FIG. 5. Therefore, aportion of the float 72, such as the head portion 84, may be receivedand retained within the interior 148 of the deformable bellows 76.

As shown in FIGS. 14-15, in the restraint position, the assembledmechanical separator 44 of the present invention includes a deformablebellows 76 engaged with the ballast 74. A portion of the float 72, suchas the head portion 84, is engaged within the interior 148 of thedeformable bellows 76. The float 72 may be secured at least partiallywithin the interior 148 of the deformable bellows 76 by the mechanicalengagement of the engagement protrusion 86 of the float 72 and therestraint shoulder 162 of the deformable bellows 76.

As shown in FIG. 15, the mechanical separator 44 can be engaged with aportion of the closure 42 in the restraint position. As shown, a portionof the closure 42, such as the boss portion 64, is received at leastpartially within the open passageway 142 of the deformable bellows 76.In one embodiment, the boss portion 64 is received within the openpassageway 142 at the upper first end 136 of the deformable bellows 76forming a liquid impermeable seal therewith.

A portion of the float 72, such as the head portion 84, may also bereceived within the open passageway 142 in the restraint position. Inone embodiment, the head portion 84 of the float 72 is received withinthe open passageway 142 at the lower second end 138 of the deformablebellows 76. The float 72 is dimensioned such that the head portion 84,having an outer diameter “d”, is greater than the inner diameter “m” ofthe open passageway 142 of the deformable bellows 76 at the upper firstend 136, as shown in FIG. 13. Accordingly, the head portion 84 of thefloat 72 cannot pass through the open passageway 142 of the deformablebellows 76 in the restraint position.

Referring again to FIG. 15, the assembled mechanical separator 44 may beurged into the bottom recess 62 of the closure 42. This insertionengages the flanges 64 of the closure 42 with the upper first end 136 ofthe deformable bellows 76. During insertion, at least a portion of theupper first end 136 of the deformable bellows 76 will deform toaccommodate the contours of the closure 42. In one embodiment, theclosure 42 is not substantially deformed during insertion of themechanical separator 44 into the bottom recess 62.

As shown in FIGS. 16-18, the mechanical separation assembly 40 includesa mechanical separator 44 and a closure 42 inserted into the open topend 50 of the tube 46, such that the mechanical separator 44 and thebottom end 58 of the closure 42 lie within the tube 46. The mechanicalseparator 44, including the deformable bellows 76, will sealingly engagethe interior of the cylindrical sidewall 52 and the open top end of thetube 46.

As shown in FIG. 17, a liquid sample is delivered to the tube 46 by thepuncture tip 164 that penetrates the septum of the top end 56 and theboss portion 64 of the closure 42. For purposes of illustration only,the liquid is blood. Blood will flow through the pierced boss portion 64of the closure, through the open passageway 142 of the deformablebellows 76, shown in FIGS. 11 and 13, over the head portion 84 of thefloat 72, and through the space between the float 72 and the opposeddepending portions 154 of the lower second end 138 of the deformablebellows 76. As shown in FIGS. 10 and 13, the opposed depending portions154 define a fluid access area 166, therebetween to allow fluid receivedfrom the puncture tip 164 to pass between the float 72 and thedeformable bellows 76 and into the closed bottom end 48 of the tube 46as shown by the arrows B, reducing pre-launch of the mechanicalseparator.

As shown in FIG. 18, once a sufficient volume of fluid has beendelivered to the tube 46, through the puncture tip 164 asabove-described, the puncture tip 164 can be removed from the closure42. In one embodiment, at least a portion of the closure 42, such as theboss portion 64, is made of a self-sealing material to form a liquidimpermeable seal once the puncture tip 164 is removed. The mechanicalseparation assembly 40 may then be subjected to accelerated rotationalforces, such as centrifuge, to separate the phases of the fluid.

Referring again to FIGS. 16-17, in use, the mechanical separator 44,particularly the deformable bellows 76, is intended to be restrainedwith the closure 42 until the mechanical separator 44 is subjected toaccelerated rotational forces, such as within a centrifuge.

As shown in FIG. 18, upon application of accelerated rotational forces,such as centrifugation, the respective phases of the blood will begin toseparate into a denser phase displaced toward the closed bottom end 58of the tube 46, and a less dense phase displaced toward the top open end50 of the tube 46, with the separated phases shown in FIG. 22. Duringcentrifugation, the mechanical separator 44 experiences a forcesufficient to disengage it from the closure 42. Once disengaged, themechanical separator 44 travels down the tube 46 toward the fluidinterface. Transition of the float 72 from the restraint position to thesealed position occurs as the mechanical separator 44 contacts andsubmerges in the fluid. As air trapped within the mechanical separator44 vents through the open passageway 142 of the deformable bellows 76,the float 72 begins to move up within the mechanical separator 44 assoon as the mechanical separator 44 contacts the fluid interface andbegins to submerge in the fluid. As the float 72 may be formed of asolid material, air is not trapped within the float 72 and thus, noadditional venting mechanism is included within the float 72. As aresult, leakage between the float 72 and the deformable bellows 76 isminimized.

Once the mechanical separator 44 is fully submerged, the float 72 andthe ballast 74 exert opposing forces on the deformable bellows 76. As aresult, the deformable bellows 76, and particularly the deformablesealing portion 140, become longer and narrower and become spacedconcentrically inward from the inner surface of the cylindrical sidewall52.

Referring to FIGS. 18-22, after the mechanical separator 44 hasdisengaged from the closure 42 and is submerged in the fluid, the outerdiameter “n” (shown in FIG. 13) of the deformable sealing portion 140 islessened, allowing the lighter phase components of the blood to slidepast the deformable sealing portion 140 and travel upwards. Likewise,heavier phase components of the blood may slide past the deformablesealing portion 140 and travel downwards. As noted above, the mechanicalseparator 44 has an overall density between the densities of theseparated phases of the blood. Upon application of applied centrifugalacceleration, the inner diameter “m” of the open passageway 142 of thedeformable bellows 76 also deforms as a result of the opposing forcesexerted upon it by the float 72 and the ballast 74. This deformationincreases the inner diameter “m” of the open passageway 142, shown inFIG. 13, to a dimension greater than the outer diameter “d” of the headportion 84 of the float 72, shown in FIG. 5, thereby allowing the headportion 84 of the float 72 to pass through the open passageway 142.Accordingly, during centrifuge, the mechanical separator 44 istransitioned from a restraint position, shown in FIGS. 14-15, to asealed position, shown in FIGS. 19-21.

Referring to FIGS. 19-21, the mechanical separator 44, including thedeformable bellows 76, ballast 74, and float 72, is shown in the sealedposition. As the inner diameter “m” of the open passageway 142 of thedeformable bellows 76 of the mechanical separator 44 is increased duringcentrifuge, the head portion 84 of the float 72 may pass therethourgh.Preferably, the inner diameter “m” of the open passageway 142 of thedeformable bellows 76 does not exceed the outer diameter “e” of theengagement protrusion 86 of the float 72 during deformation. Even morepreferably, the inner diameter “m” of the open passageway 142 does notexceed the outer diameter “b” of the second stepped section 94 of thefloat 72 during deformation. Because the float 72 is made of a naturallybuoyant material, the float 72 is urged upwardly as indicated by thearrow A.

Once centrifuge is ceased, the inner diameter “m” of the open passageway142 returns to the unbiased position and engages the float 72 about theneck portion 88 in the sealed position. In one embodiment, thedeformable bellows 76 form a liquid impermeable seal about the neckportion 88 of the float 72 through the open passageway 142 in the sealedposition. In the sealed position, at least a portion of the float 72,such as the head portion 84, is positioned at a location exterior 168 tothe deformable bellows 76, such as at a location exterior 168 to theinterior 148 of the deformable bellows 76. In this embodiment, the headportion 84 may be positioned at an exterior location 168 that islongitudinally displaced from the deformable bellows 76 along thelongitudinal axis L₃ of the mechanical separator 44 in the sealedposition. Because the float 72 of the mechanical separator 44 is buoyantin fluid, when the mechanical separator 44 is oriented as shown in FIGS.16-18, the head portion 84 of the float 72 may be positioned below theupper first end 136 of the deformable bellows 76, shown in FIG. 15, inthe restraint position, and positioned above the upper first end 136 ofthe deformable bellows 76, shown in FIGS. 19-21, in the sealed position.

Referring to FIG. 22, after centrifuge and the transition of themechanical separator 44 from the restraint position to the sealedposition, the mechanical separator 44 will stabilize in a positionwithin the tube 46 of the mechanical separation device 40, such that theheavier phase components 170 will be located between the mechanicalseparator 44 and the closed bottom end 58 of the tube 46, while thelighter phase components 172 will be located between the mechanicalseparator 44 and the top end of the tube 50. After this stabilized statehas been reached, the centrifuge will be stopped and the deformablebellows 76, particularly the deformable sealing portion 140, willresiliently return to its unbiased state and into sealing engagementwith the interior of the cylindrical sidewall 52 of the tube 46. Theformed liquid phases may then be accessed separately for analysis.

Although the above invention has been described with specific referenceto certain configurations, it is contemplated herein that variousalternative structures may be employed without departing from the spiritof the claims herein. For example, as shown in FIGS. 23-24, although theprevious description of the invention was made with reference to aclosure having a bottom recess and/or a boss portion, the mechanicalseparator 244 can be configured to include a standard closure 242 havinga conventionally sloped bottom surface 246. In this configuration, thedeformable bellows 276, having an open passageway 243, is held inposition adjacent the standard closure 242 by an interference fitbetween the interior wall 250 of the tube 252 and the outer surface 254of the deformable bellows 276. Optionally, a small annular protrusion258 in the interior wall 250 of the tube 252 may be employed to furtherincrease the interference between the deformable bellows 276 and thetube 252. The ballast 290 is engaged with at least a portion of thedeformable bellows 276. Also shown in FIGS. 23-24, it is contemplatedherein that various configurations of the float 272 may also beemployed, provided at least a portion of float 272, such as a headportion 280, is transitioned from a position within the interior of thedeformable bellows 276 in restraint position, shown in FIG. 23, to aposition exterior to the deformable bellows 276 in the sealed position,shown in FIG. 24.

As shown in FIGS. 25-26, the mechanical separator 344 can be engagedwith a closure 342 having a luer collar 320, which may be engaged intothe underside of the closure 342. In one embodiment, the luer collar 320may be snap-engaged into the underside 370 of the closure 342. In use,when the mechanical separator 344 including a deformable bellows 376, aballast 390 engaged with a portion of the deformable bellows 376, and afloat 372 also engaged with a portion of the deformable bellows 376, issubject to centrifuge, the luer collar 320 may release from theunderside 370 of the closure 342 along with the mechanical separator344. Upon transition from the restraint position, shown in FIG. 25, tothe sealed position, shown in FIG. 26, the head portion 384 of the float372 of the mechanical separator 344 transitions from a position at leastpartially interior to the deformable bellows 376 to a position exteriorto the deformable bellows 376 and into the luer collar 320.

As shown in FIG. 27, the mechanical separator 444, including adeformable bellows 476, a ballast 490 engaged with a portion of thedeformable bellows 476, and a float 472 also engaged with a portion ofthe deformable bellows 476, may be inserted into a tube 446 having atube insert 450. The tube insert 450 can be any appropriate deviceinserted into the tube 446, such as circumferentially disposed about aportion of the mechanical separator 444, to prevent premature release ofthe mechanical separator 444 from the tube insert 450 of the closure442. In one embodiment, the tube insert 450 can be circumferentiallydisposed about a portion of the deformable bellows 476 to provideadditional interference with the tube 476.

Alternatively, as shown in FIG. 28, the mechanical separator 544,including a deformable bellows 576, a ballast 590 engaged with a portionof the deformable bellows 576, and a float 572 also engaged with aportion of the deformable bellows 576 may be engaged with a retainingcollar 550 that is permanently affixed to the underside of the closure542. In one embodiment, the deformable bellows 576 is held fixedrelative to the closure 542 during shipping and handling. The interiordiameter “r” of the retaining collar 550 is sufficiently sized to allowaccess of a puncture tip for closure sampling after centrifugation (notshown), therethrough.

As shown in FIGS. 29-30, the mechanical separator 644 may also include adeformable bellows 676, a ballast 690 engaged with a portion of thedeformable bellows 676, and a float 672 also engaged with a portion ofthe deformable bellows 676. In this embodiment, the deformable bellows676 are biased over a boss portion 646 of the closure 642. In therestraint position, as shown in FIG. 29, the inner diameter “s” of theopen passageway 652 of the deformable bellows 676 is enlarged toaccommodate the boss portion 646. In the sealed position, shown in FIG.30, the head portion 684 of the float 672 passes through the openpassageway 652 to a location exterior to the deformable bellows 676 andis sealed therein by the unbiased diameter of the passageway 652.Optionally, the ballast 690 may include a shoulder 630 and the float 672may include an engagement protrusion 632 for restraining the float 672within the mechanical separator 644 during shipment in the restraintposition.

As shown in FIGS. 31-32, the mechanical separator 744 may include adeformable bellows 776, a ballast 790 engaged with a portion of thedeformable bellows 776, and a float 772 also engaged with a portion ofthe deformable bellows 776. The closure 742 may include a ring 750adjacent the contact surface 752 to further secure the deformablebellows 776 to the closure 742 in the restraint position, shown in FIG.31. In this configuration, introduction of fluid, such as blood, causesthe float 772 of the mechanical separator 744 to rise, andcentrifugation causes the deformable bellows 776 to separate from theclosure 742 and transitioning the mechanical separator 744 from therestraint position, shown in FIG. 31, to the closed position, shown inFIG. 32.

Alternatively, as shown in FIGS. 33-34, the mechanical separator 844 mayinclude a deformable bellows 876, a ballast 890 engaged with a portionof the deformable bellows 876, and a substantially spherical float 872.In this embodiment, the open passageway 870 of the deformable bellows876 includes protrusions 882 substantially corresponding to the outerdiameter of the spherical float 872. In the restraint position, shown inFIG. 33, the spherical float 872 is positioned within the interior 840of the mechanical separator 844. In the sealed position, shown in FIG.34, the spherical float 872 includes a first portion 835 transitioned atleast partially exterior to the interior 840 of the mechanical separator844. In one embodiment, the spherical float 872 forms a seal with theprotrusions 882 of the deformable bellows 876.

The mechanical separator of the present invention includes a float thatis transitionable from a restraint position to a sealed position as thefloat and ballast exert opposing forces on the deformable bellows,thereby allowing the float to be received within the deformable bellows.Thus, in use, the mechanical separator of the present inventionminimizes device pre-launch and reduces sample pooling under the closureby providing an open passageway within the bellows. Additionally, thereduced clearance between the exterior of the float and the interior ofthe ballast minimizes the loss of trapped fluid phases, such as serumand plasma.

Although the present invention has been described in terms of amechanical separator disposed within the tube adjacent the open end, itis also contemplated herein that the mechanical separator may be locatedat the bottom of the tube, such as affixed to the bottom of the tube.This configuration can be particularly useful for plasma applications inwhich the blood sample does not clot, because the mechanical separatoris able to travel up through the sample during centrifugation.

While the present invention is described with reference to severaldistinct embodiments of a mechanical separator assembly and method ofuse, those skilled in the art may make modifications and alterationswithout departing from the scope and spirit. Accordingly, the abovedetailed description is intended to be illustrative rather thanrestrictive. For example, while the assembly described above relates toa biological sample tube, other types of sample containers may be used.In addition, while various configurations of the components have beenprovided above, it should be noted that other shapes and dimensions maybe implemented.

The invention claimed is:
 1. A mechanical separator comprising: a floathaving a first portion and a second portion; a ballast circumferentiallydisposed about a section of the float and longitudinally moveable withrespect to the float; and a deformable bellows defining an openpassageway extending between a first end of the deformable bellows and asecond end of the deformable bellows, the ballast engaged with thedeformable bellows between the first end and the second end, and atleast a portion of the float transitionable from a restraint position toa sealed position through the first end of the deformable bellows,wherein the first end of the deformable bellows engages the float tomaintain the float in the sealed position, and wherein the first portionof the float is positioned within the interior of the deformable bellowsin the restraint position, and at least a portion of the first portionof the float is positioned through the open passageway of the deformablebellows in the sealed position.
 2. The mechanical separator of claim 1,wherein the float has a first density, and the ballast has a seconddensity which is greater than the first density of the float.
 3. Themechanical separator of claim 1, wherein the mechanical separator isoriented such that the first portion of the float is positioned belowthe first end of the deformable bellows in the restraint position, andthe first portion of the float is positioned above the first end of thedeformable bellows in the sealed position.
 4. The mechanical separatorof claim 1, wherein the transition from the restraint position to thesealed position occurs as the float and ballast exert opposing forces onthe deformable bellows.
 5. The mechanical separator of claim 4, whereinthe transition from the restraint position to the sealed positionfurther includes advancing the float within the open passageway of thedeformable bellows.
 6. The mechanical separator of claim 1, wherein thefloat comprises an engagement protrusion and the deformable bellowscomprises a restraint shoulder, the engagement protrusion of the floatrestrained within the deformable bellows by the restraint shoulder. 7.The mechanical separator of claim 1, wherein the float comprises a headportion and a body portion, the body portion comprising a first sectionhaving a first diameter and a second stepped section having a seconddiameter, the second diameter greater than the first diameter.
 8. Themechanical separator of claim 1, wherein the float is solid.
 9. Themechanical separator of claim 1, wherein the ballast comprises aninterlock recess for accommodating a portion of the deformable bellowsfor attachment thereto.
 10. The mechanical separator of claim 1, whereinthe ballast comprises an exterior surface and defines an annularshoulder circumferentially disposed within the exterior surface.
 11. Themechanical separator of claim 1, wherein at least a portion of the firstend of the deformable bellows is structured for receipt within aclosure.
 12. The mechanical separator of claim 11, wherein at least aportion of the first end of the deformable bellows is structured toreceive a portion of the closure therein.
 13. The mechanical separatorof claim 11, wherein the float and deformable bellows form a liquidimpermeable seal in the sealed position.
 14. The mechanical separator ofclaim 1, wherein the float comprises polypropylene, the ballastcomprises polyethylene terephthalate, and the deformable bellowscomprises a thermoplastic elastomer.
 15. A separation assembly forenabling separation of a fluid sample into first and second phases,comprising: a tube, having an open end, an opposing end, and a sidewallextending therebetween; a closure adapted for a sealing engagement withthe open end of the tube, the closure defining a recess; and amechanical separator releaseably engaged within the recess, themechanical separator comprising: a float having a first portion and asecond portion, the float having a first density; a ballastcircumferentially disposed about a section of the float andlongitudinally moveable with respect to the float, the ballast having asecond density greater than the first density of the float; and adeformable bellows defining an open passageway extending between a firstend of the deformable bellows and a second end of the deformablebellows, the ballast engaged with the deformable bellows between thefirst end and the second end, and at least a portion of the floattransitionable from a restraint position to a sealed position throughthe first end of the deformable bellows, wherein the first end of thedeformable bellows engages the float to maintain the float in the sealedposition, and wherein the first portion of the float is positionedwithin the interior of the deformable bellows in the restraint position,and at least a portion of the first portion of the float is positionedthrough the open passageway of the deformable bellows in the sealedposition.
 16. The separation assembly of claim 15, wherein themechanical separator is oriented such that the first portion of thefloat is positioned below the first end of the deformable bellows in therestraint position, and the first portion of the float is positionedabove the first end of the deformable bellows in the sealed position.17. The separation assembly of claim 15, wherein the float comprises anengagement protrusion and the deformable bellows comprises a restraintshoulder, the engagement protrusion of the float restrained within thedeformable bellows by the restraint shoulder.
 18. The separationassembly of claim 15, wherein the transition from the restraint positionto the sealed position occurs upon deformation of the deformable bellowsand receipt of the float within the passageway of the deformablebellows.